The present invention relates to a structure of mounting an intermediate wall in a dual cavity toroidal continuously variable transmission (CVT) and a method of assembling the dual cavity toroidal CVT with the intermediate wall.
FIGS. 38 and 39 show a dual cavity toroidal CVT of a related art. As illustrated in FIG. 38, the dual cavity toroidal CVT includes transmission case 1, main shaft 10 rotatably supported within transmission case 1, two toroidal speed change units 2 and 3 spaced from each other on main shaft 10, and intermediate wall 31 between toroidal speed change units 2 and 3. Intermediate wall 31 supports a middle portion of main shaft 10 between toroidal speed change units 2 and 3. Intermediate wall 31 is fixed to inner circumferential flange 32 inwardly extending from an inner circumferential surface of transmission case 1 by means of fastening bolts 33 extending in an axial direction of main shaft 10. Inner circumferential flange 32 mates with an outer circumferential portion of intermediate wall 31. Intermediate wall 31 is constituted of front and rear halves joined together. Each fastening bolt 33 is inserted into mount holes which are formed in the front half of intermediate wall 31 and inner circumferential flange 32, respectively. Intermediate wall 31 is thus secured to transmission case 1.
Front toroidal speed change unit 2 and rear toroidal speed change unit 3 are coaxially arranged within transmission case 1. Each toroidal speed change unit 2, 3 includes coaxially arranged input disk 4, 5 and output disk 6, 7, and power rollers 8, 9 disposed between input and output disks 4 and 6, 5 and 7. Input and output disks 4-7 have common rotation axis O3 aligned with the axis of main shaft 10. Input and output disks 4-7 are supported on main shaft 10 so as to be rotatable about rotation axis O3. Input disks 4 and 5 are rotatably engaged with main shaft 10 via ball spline 11 and axially slidable on main shaft 10. Input disk 5 is prevented from being removed from main shaft 10 by loading nut 12 screwed on main shaft 10 and disc spring 29 adjacent to loading nut 12. Output disks 6 and 7 are connected with each other via hollow output shaft 13 rotatably supported on main shaft 10. Output disks 6 and 7 are arranged back-to-back in an axially spaced relation to each other, between which intermediate wall 31 is interposed. Power rollers 8 and 9 transmit power between input and output disks 4-7 via a traction oil film. Power rollers 8 and 9 are diametrically opposed to each other with respect to rotation axis O3 of input and output disks 4-7. Power rollers 8 and 9 are supported on trunnions 14 and 15 by linear bearing BRG so as to be movable in the direction of rotation axis O3 and be rotatable about rotation axis O1.
FIG. 39 shows front toroidal speed change unit 2, in which only two front trunnions 14 are illustrated. Front and rear trunnions 14 and 15 have upper ends which are disposed near top wall 1A of transmission case 1 and connected with four corners of a generally rectangular plate-shaped upper link 16. Lower ends of trunnions 14 and 15 are connected with four corners of a generally rectangular plate-shaped lower link 17. A combined joint formed by spherical joint 18 and roller bearing 19 is used for the linkage of trunnions 14 and 15, so that trunnions 14 and 15 are rotatably and angularly moveable relative to upper and lower links 16 and 17. Upper and lower links 16 and 17 hold trunnions 14 and 15 in place such that power rollers 8 and 9 can be prevented from being pushed out from the cavity formed by input and output disks 4, 6 and 5, 7 by a loading force applied to input and output disks 4, 6 and 5, 7 as explained later. Upper link supports 20 and 21 are-mounted to transmission case 1 between the upper ends of front trunnions 14 and between the upper ends of rear trunnions 15 by means of bolts 22 and 23, respectively. Pins 27 extend from upper link supports 20 and 21 into upper link 16 in the direction of rotation axis O3 as shown in FIG. 39. Lower link supports 24 and 25 are mounted to transmission case 1 between the lower ends of front trunnions 14 and between the lower ends of rear trunnions 15 by means of bolts 26. Pins 28 extend through lower link supports 24 and 25 into lower link 17 in the direction of rotation axis O3 as shown in FIG. 39. Upper and lower links 16 and 17 are thus supported on transmission case 1 via pins 27 and 28, respectively. Servo piston 42 is coaxially connected with the lower ends of front and rear trunnions 14 and 15 and operates trunnions 14 and 15 to synchronously stroke or offset in the same phase (the same speed-change direction).
Loading cam 38 transmits input rotation to front input disk 4 and rear input disk 5 via main shaft 10, and at the same time, applies a thrust load corresponding to the transmitted torque to input disk 4 to urge front input disk 4 toward front output disk 6. Reaction force produced is transmitted to rear input disk 5 via main shaft 10, loading nut 12 and disc spring 29, so that rear input disk 5 is urged toward rear output disk 7. Power rollers 8 and 9 are pressed by corresponding input and output disks 4, 6 and 5, 7 undergoing the thrust load. Power rollers 8 and 9 are rotated about rotation axis O1 upon rotation of input disks 4 and 5 and transmit the rotation to output disks 6 and 7. The rotation is then transmitted to output gear 34 integrally formed with output shaft 13, counter gear 30 meshed with output gear 34, and then a counter shaft connected with counter gear 30. Output gear 34 is located on output shaft 13 between output disks 6 and 7 and accommodated within intermediate wall 31.
Power rollers 8 and 9 are driven via trunnions 14 and 15 by servo piston 42. Specifically, when trunnions 14 and 15 are allowed to synchronously move along pivot axis O2 at the identical stroke, power rollers 8 and 9 move from initial positions shown in FIG. 39 along pivot axis O2. As a result, rotation axis O1 is offset from rotation axis O3 of input and output disks 4-7, and power rollers 8 and 9 are synchronously pivoted about pivot axis O2 with the identical phase by component of force of the rotation of input disks 4 and 5. This causes continuous change in size of circles traced by contact points between input disks 4 and 5 and power rollers 8 and 9 and circles traced by contact points between power rollers 8 and 9 and output disks 6 and 7. Gear ratio between input and output disks 4 and 6 and gear ratio between input and output disks 5 and 7 can be continuously varied while being kept equal to each other. U.S. Pat. No. 5,902,208 (corresponding to Japanese Patent Application First Publication No. 9-310741) discloses such a dual cavity toroidal CVT as described above, which is incorporated by reference herein. Japanese Patent Application First Publication No. 2001-12574 and International Application Publication No. WO 01/42684 A1 (corresponding to Japanese Patent Application First Publication No. 2001-165265) disclose such a power roller supporting structure as described above, which are incorporated by reference herein.
Upon assembly, transmission case 1 is placed at an upset state such that a bottom opening thereof on the oil pan side is directed upward. Upper link 16 and output shaft 13 carrying output disks 6 and 7, gears 30 and 34 and intermediate wall 31 are inserted into transmission case 1 through the bottom opening. Main shaft 10 with front input disk 4 is mounted into output shaft 13 and rear input disk 5 is mounted onto main shaft 10. Left and right trunnions-synchronizing wires 35 (see FIG. 39), trunnions 14 and 15 with power rollers 8 and 9, lower link 17, and front and rear trunnions-synchronizing wires 36 (see FIG. 39) are in order inserted into transmission case 1. Bolts 33 are inserted from a front opening (on the left side of FIG. 38) of transmission case 1 into transmission case 1 and screwed into the respective mount holes of intermediate wall 31 and inner circumferential flange 32 of transmission case 1. Intermediate wall 31 is thus secured to transmission case 1.